Original ArticleDevelopment and validation of a scoring system for the identification of pleural exudates of cardiac origin☆
Introduction
Pleural effusions are common in patients with decompensated heart failure (HF). The identification of cardiac effusions is usually considered to be an easy task and the performance of a pleural tap is unnecessary in most clinical situations. However, the diagnosis of cardiac effusions is not always straightforward, even when pleural fluid data are available [6]. For example, one study called into question the physicians' ability to correctly identify transudates prior to thoracentesis by showing that the initial clinical presumption failed 44% of the time [13]. In addition, Light's criteria [4], which are considered the gold standard for transudate-exudate differentiation in every-day practice, leave nearly 30% of cardiac effusions erroneously labeled as exudates [1], [10]. No consensus exists on the best way to reclassify the latter as true transudates [7]. Although the identification of cardiac effusions, in general, and false cardiac exudates, in particular, may be greatly improved with the measurement of natriuretic peptides [9], these biomarkers of HF are not always used as an initial diagnostic test for the work-up of pleural effusions and variabilities in laboratory methodologies and proper cutoffs should be considered.
The goal of this study was to provide a practical tool based on the combination of simple clinical, radiological and pleural fluid biochemical findings for the accurate identification of exudative effusions (according to Light's criteria) secondary to HF, when natriuretic peptides are not immediately available. To this end, an easily applicable scoring model was devised and validated.
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Study population
A retrospective review was done of the medical charts of all consecutive patients who were subjected to a diagnostic thoracentesis at the Arnau de Vilanova University Hospital (Lleida, Spain) from 1994 to 2016, and whose pleural fluids met Light's criteria for exudates [4]. This 450-bed tertiary care facility serves a population of approximately 450,000 people. Recruited patients from this hospital aided in the generation of a scoring system for discriminating between cardiac and non-cardiac
Patients characteristics
A total of 3182 adult patients with exudative pleural effusions, of which 276 (8.7%) were related to HF, composed the derivation sample. The validation sample was comprised of 1165 patients with a similar proportion of cardiac (107, 9.2%) and non-cardiac effusions (1058, 90.8%) as the derivation set (p = 0.60). Also, the median age and sex of cardiac and non-cardiac effusions were comparable between both cohorts. These and other baseline characteristics are displayed in Table 1, Table 2.
Diagnostic accuracy of individual findings for cardiac effusions (derivation set)
The
Discussion
This study presents a clinical scoring model for identifying patients with pleural effusions due to HF, which should only be applied when pleural fluids meet Light's criteria for exudates. This score exceeded the discriminative capabilities of what is routinely recommended in clinical practice, namely the protein and albumin gradients in isolation. Overall, the scoring system may represent a useful tool in the identification of cardiac pleural effusions miscategorized by standard criteria, when
Conclusions
We derived and validated a simple rule which should be viewed as a diagnostic weight to estimate the probability of HF in patients whose pleural fluids meet Light's criteria for exudate. A prospective validation of our results is warranted.
Specific author contributions
J.M.P. and L.F. had full access to all the data and take full responsibility for the integrity of the data and the accuracy of the data analysis. J.M.P. contributed to the design of the study, data interpretation and drafting the manuscript. L.F., C.C., L.V., A.E. and S.B. contributed to data acquisition. S.B. contributed to data analysis and interpretation. R.L. provided revision for important intellectual content. All authors approved the final version of the manuscript for publication.
Financial/nonfinancial disclosures
None declared.
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Authors have no conflict of interests to disclose.